Description: By using our knowledge of supplementary, adjacent, and vertical angles, we can solve problems involving the intersection of two lines. Including this one! Created by Sal Khan. And let's say we know, we're given, that this angle right over here. Let's say that we know that the measure of this angle right over here, angle BED, let's say that we know that measure is 70 degrees. They're next to each other and they form a straight angle when you take their outer sides.*Teacher Advisor is 100% free.